The proposed project will examine the orientation and organizational structure of two phage T4-coded integral membrane proteins. Mutations of the structural genes for these proteins are expressed as a phenotype called DNA-delay. Our studies have shown that these mutations also causes a concomittant and equal decrease in the rate of synthesis of deoxyribonucleotides. We seek 1) to isolate the two membrane proteins and to characterize their terminal amino acid segments and hydrophobic cores by proteolytic enzymes and chemical methods; 2) to study their orientation in the bacterial membrane and in synthetic phospholipid vesicles using proteolytic enzymes and labeled specific antibodies, and 3) to carry out cross-linking studies to determine their interaction with each other in the membrane, with peripheral proteins associated with the membrane and with the phospholipids of the bilayer.